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Kaopectate Side Effects

Generic Name: bismuth subsalicylate

Note: This document contains side effect information about bismuth subsalicylate. Some of the dosage forms listed on this page may not apply to the brand name Kaopectate.

For the Consumer

Applies to bismuth subsalicylate: oral suspension, oral tablet, oral tablet chewable

Along with its needed effects, bismuth subsalicylate (the active ingredient contained in Kaopectate) may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention.

Check with your doctor immediately if any of the following side effects occur while taking bismuth subsalicylate:

In some patients bismuth subsalicylate may cause dark tongue and/or grayish black stools. This is only temporary and will go away when you Stop taking bismuth subsalicylate.

  • Anxiety
  • any loss of hearing
  • confusion
  • constipation (severe)
  • diarrhea (severe or continuing)
  • difficulty in speaking or slurred speech
  • dizziness or lightheadedness
  • drowsiness (severe)
  • fast or deep breathing
  • headache (severe or continuing)
  • increased sweating
  • increased thirst
  • mental depression
  • muscle spasms (especially of face, neck, and back)
  • muscle weakness
  • nausea or vomiting (severe or continuing)
  • ringing or buzzing in ears (continuing)
  • stomach pain (severe or continuing)
  • trembling
  • uncontrollable flapping movements of the hands (especially in elderly patients) or other uncontrolled body movements
  • vision problems

For Healthcare Professionals

Applies to bismuth subsalicylate: compounding powder, oral suspension, oral tablet, oral tablet chewable

Nervous system

Rare (less than 0.1%): Myoclonic encephalopathy
Frequency not reported: Weakness, fatigue, depression, anxiety, irritability, insomnia, unsteady gait, motor incoordination, loss of memory, jerky movements, mental confusion, disorientation, difficulty in walking and speaking, tremor, myoclonic jerks, incontinence[Ref]

Nervous system toxicity is a common feature of bismuth toxicity. Bismuth toxicity is characterized by the insidious onset of weakness and fatigue, depression, anxiety, irritability, insomnia, unsteady gait, motor incoordination, loss of memory, and jerky movements. Acute toxicity may result in the development of mental confusion, disorientation, difficulty in walking and speaking, tremor, myoclonic jerks, and incontinence.

Myoclonic encephalopathy has occurred in patients who have ingested bismuth for several months to years, but the incidence is very rare. Recovery of patients from bismuth encephalopathy may take several months following discontinuation of use. Bismuth encephalopathy has generally been reported in patients ingesting salts other than subsalicylate.[Ref]


Salicylism has been reported in patients who chronically ingest bismuth subsalicylate (the active ingredient contained in Kaopectate) Common complaints include vertigo, diminished hearing, lethargy, CNS dysfunction, confusion, tinnitus, vomiting, and abdominal pain. Patients may present with respiratory alkalosis and metabolic acidosis, azotemia, and hypoprothrombinemia and platelet dysfunction. The elderly may be particularly vulnerable to the development of salicylism.[Ref]

Frequency not reported: Salicylism[Ref]


Very common (10% or more): Black stool
Common (1% to 10%): Black tongue
Frequency not reported: Nausea, vomiting[Ref]


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13. Bierer DW "Bismuth subsalicylate: history, chemistry, and safety." Rev Infect Dis 12 Suppl 1 (1990): s3-8

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Some side effects of Kaopectate may not be reported. Always consult your doctor or healthcare specialist for medical advice. You may also report side effects to the FDA.

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